The knowledge of the physical and chemical properties of trans-Neptunian objects (TNOs) is still incomplete and confused. To investigate their physical properties, we are continuing the TNO observational program started in 1997 at ESO in La Silla, Chile with the 3.5 m New Technology Telescope. In February 1999, broadband optical colors were obtained for eight new objects: 1993 FW, 1995 HM5, 1997 CQ29, 1997 CS29, 1997 CT29, 1997 CU29, 1998 FS144, and 1998 WH24. Particular attention has been paid to the observations and data reduction of these faint objects. These new data increase the available statistical sample and will help us to understand the surface properties and the mechanisms of the surface modification of the TNOs. The observed objects present a wide spread of colors. The color distribution does not show any bimodality. Knowledge of the colors of a large number of these objects is important to understand this population, which represents an important reservoir of primordial material.